1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/seccomp.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/kthread.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/proc_fs.h> 52 #include <linux/profile.h> 53 #include <linux/rmap.h> 54 #include <linux/ksm.h> 55 #include <linux/acct.h> 56 #include <linux/tsacct_kern.h> 57 #include <linux/cn_proc.h> 58 #include <linux/freezer.h> 59 #include <linux/delayacct.h> 60 #include <linux/taskstats_kern.h> 61 #include <linux/random.h> 62 #include <linux/tty.h> 63 #include <linux/blkdev.h> 64 #include <linux/fs_struct.h> 65 #include <linux/magic.h> 66 #include <linux/perf_event.h> 67 #include <linux/posix-timers.h> 68 #include <linux/user-return-notifier.h> 69 #include <linux/oom.h> 70 #include <linux/khugepaged.h> 71 #include <linux/signalfd.h> 72 #include <linux/uprobes.h> 73 74 #include <asm/pgtable.h> 75 #include <asm/pgalloc.h> 76 #include <asm/uaccess.h> 77 #include <asm/mmu_context.h> 78 #include <asm/cacheflush.h> 79 #include <asm/tlbflush.h> 80 81 #include <trace/events/sched.h> 82 83 #define CREATE_TRACE_POINTS 84 #include <trace/events/task.h> 85 86 /* 87 * Protected counters by write_lock_irq(&tasklist_lock) 88 */ 89 unsigned long total_forks; /* Handle normal Linux uptimes. */ 90 int nr_threads; /* The idle threads do not count.. */ 91 92 int max_threads; /* tunable limit on nr_threads */ 93 94 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 95 96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 97 98 #ifdef CONFIG_PROVE_RCU 99 int lockdep_tasklist_lock_is_held(void) 100 { 101 return lockdep_is_held(&tasklist_lock); 102 } 103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 104 #endif /* #ifdef CONFIG_PROVE_RCU */ 105 106 int nr_processes(void) 107 { 108 int cpu; 109 int total = 0; 110 111 for_each_possible_cpu(cpu) 112 total += per_cpu(process_counts, cpu); 113 114 return total; 115 } 116 117 void __weak arch_release_task_struct(struct task_struct *tsk) 118 { 119 } 120 121 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 122 static struct kmem_cache *task_struct_cachep; 123 124 static inline struct task_struct *alloc_task_struct_node(int node) 125 { 126 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 127 } 128 129 static inline void free_task_struct(struct task_struct *tsk) 130 { 131 kmem_cache_free(task_struct_cachep, tsk); 132 } 133 #endif 134 135 void __weak arch_release_thread_info(struct thread_info *ti) 136 { 137 } 138 139 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 140 141 /* 142 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 143 * kmemcache based allocator. 144 */ 145 # if THREAD_SIZE >= PAGE_SIZE 146 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 147 int node) 148 { 149 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 150 THREAD_SIZE_ORDER); 151 152 return page ? page_address(page) : NULL; 153 } 154 155 static inline void free_thread_info(struct thread_info *ti) 156 { 157 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 158 } 159 # else 160 static struct kmem_cache *thread_info_cache; 161 162 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 163 int node) 164 { 165 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 166 } 167 168 static void free_thread_info(struct thread_info *ti) 169 { 170 kmem_cache_free(thread_info_cache, ti); 171 } 172 173 void thread_info_cache_init(void) 174 { 175 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 176 THREAD_SIZE, 0, NULL); 177 BUG_ON(thread_info_cache == NULL); 178 } 179 # endif 180 #endif 181 182 /* SLAB cache for signal_struct structures (tsk->signal) */ 183 static struct kmem_cache *signal_cachep; 184 185 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 186 struct kmem_cache *sighand_cachep; 187 188 /* SLAB cache for files_struct structures (tsk->files) */ 189 struct kmem_cache *files_cachep; 190 191 /* SLAB cache for fs_struct structures (tsk->fs) */ 192 struct kmem_cache *fs_cachep; 193 194 /* SLAB cache for vm_area_struct structures */ 195 struct kmem_cache *vm_area_cachep; 196 197 /* SLAB cache for mm_struct structures (tsk->mm) */ 198 static struct kmem_cache *mm_cachep; 199 200 static void account_kernel_stack(struct thread_info *ti, int account) 201 { 202 struct zone *zone = page_zone(virt_to_page(ti)); 203 204 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 205 } 206 207 void free_task(struct task_struct *tsk) 208 { 209 account_kernel_stack(tsk->stack, -1); 210 arch_release_thread_info(tsk->stack); 211 free_thread_info(tsk->stack); 212 rt_mutex_debug_task_free(tsk); 213 ftrace_graph_exit_task(tsk); 214 put_seccomp_filter(tsk); 215 arch_release_task_struct(tsk); 216 free_task_struct(tsk); 217 } 218 EXPORT_SYMBOL(free_task); 219 220 static inline void free_signal_struct(struct signal_struct *sig) 221 { 222 taskstats_tgid_free(sig); 223 sched_autogroup_exit(sig); 224 kmem_cache_free(signal_cachep, sig); 225 } 226 227 static inline void put_signal_struct(struct signal_struct *sig) 228 { 229 if (atomic_dec_and_test(&sig->sigcnt)) 230 free_signal_struct(sig); 231 } 232 233 void __put_task_struct(struct task_struct *tsk) 234 { 235 WARN_ON(!tsk->exit_state); 236 WARN_ON(atomic_read(&tsk->usage)); 237 WARN_ON(tsk == current); 238 239 security_task_free(tsk); 240 exit_creds(tsk); 241 delayacct_tsk_free(tsk); 242 put_signal_struct(tsk->signal); 243 244 if (!profile_handoff_task(tsk)) 245 free_task(tsk); 246 } 247 EXPORT_SYMBOL_GPL(__put_task_struct); 248 249 void __init __weak arch_task_cache_init(void) { } 250 251 void __init fork_init(unsigned long mempages) 252 { 253 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 254 #ifndef ARCH_MIN_TASKALIGN 255 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 256 #endif 257 /* create a slab on which task_structs can be allocated */ 258 task_struct_cachep = 259 kmem_cache_create("task_struct", sizeof(struct task_struct), 260 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 261 #endif 262 263 /* do the arch specific task caches init */ 264 arch_task_cache_init(); 265 266 /* 267 * The default maximum number of threads is set to a safe 268 * value: the thread structures can take up at most half 269 * of memory. 270 */ 271 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 272 273 /* 274 * we need to allow at least 20 threads to boot a system 275 */ 276 if (max_threads < 20) 277 max_threads = 20; 278 279 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 280 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 281 init_task.signal->rlim[RLIMIT_SIGPENDING] = 282 init_task.signal->rlim[RLIMIT_NPROC]; 283 } 284 285 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 286 struct task_struct *src) 287 { 288 *dst = *src; 289 return 0; 290 } 291 292 static struct task_struct *dup_task_struct(struct task_struct *orig) 293 { 294 struct task_struct *tsk; 295 struct thread_info *ti; 296 unsigned long *stackend; 297 int node = tsk_fork_get_node(orig); 298 int err; 299 300 tsk = alloc_task_struct_node(node); 301 if (!tsk) 302 return NULL; 303 304 ti = alloc_thread_info_node(tsk, node); 305 if (!ti) 306 goto free_tsk; 307 308 err = arch_dup_task_struct(tsk, orig); 309 if (err) 310 goto free_ti; 311 312 tsk->stack = ti; 313 314 setup_thread_stack(tsk, orig); 315 clear_user_return_notifier(tsk); 316 clear_tsk_need_resched(tsk); 317 stackend = end_of_stack(tsk); 318 *stackend = STACK_END_MAGIC; /* for overflow detection */ 319 320 #ifdef CONFIG_CC_STACKPROTECTOR 321 tsk->stack_canary = get_random_int(); 322 #endif 323 324 /* 325 * One for us, one for whoever does the "release_task()" (usually 326 * parent) 327 */ 328 atomic_set(&tsk->usage, 2); 329 #ifdef CONFIG_BLK_DEV_IO_TRACE 330 tsk->btrace_seq = 0; 331 #endif 332 tsk->splice_pipe = NULL; 333 tsk->task_frag.page = NULL; 334 335 account_kernel_stack(ti, 1); 336 337 return tsk; 338 339 free_ti: 340 free_thread_info(ti); 341 free_tsk: 342 free_task_struct(tsk); 343 return NULL; 344 } 345 346 #ifdef CONFIG_MMU 347 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 348 { 349 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 350 struct rb_node **rb_link, *rb_parent; 351 int retval; 352 unsigned long charge; 353 struct mempolicy *pol; 354 355 down_write(&oldmm->mmap_sem); 356 flush_cache_dup_mm(oldmm); 357 uprobe_dup_mmap(oldmm, mm); 358 /* 359 * Not linked in yet - no deadlock potential: 360 */ 361 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 362 363 mm->locked_vm = 0; 364 mm->mmap = NULL; 365 mm->mmap_cache = NULL; 366 mm->free_area_cache = oldmm->mmap_base; 367 mm->cached_hole_size = ~0UL; 368 mm->map_count = 0; 369 cpumask_clear(mm_cpumask(mm)); 370 mm->mm_rb = RB_ROOT; 371 rb_link = &mm->mm_rb.rb_node; 372 rb_parent = NULL; 373 pprev = &mm->mmap; 374 retval = ksm_fork(mm, oldmm); 375 if (retval) 376 goto out; 377 retval = khugepaged_fork(mm, oldmm); 378 if (retval) 379 goto out; 380 381 prev = NULL; 382 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 383 struct file *file; 384 385 if (mpnt->vm_flags & VM_DONTCOPY) { 386 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 387 -vma_pages(mpnt)); 388 continue; 389 } 390 charge = 0; 391 if (mpnt->vm_flags & VM_ACCOUNT) { 392 unsigned long len = vma_pages(mpnt); 393 394 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 395 goto fail_nomem; 396 charge = len; 397 } 398 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 399 if (!tmp) 400 goto fail_nomem; 401 *tmp = *mpnt; 402 INIT_LIST_HEAD(&tmp->anon_vma_chain); 403 pol = mpol_dup(vma_policy(mpnt)); 404 retval = PTR_ERR(pol); 405 if (IS_ERR(pol)) 406 goto fail_nomem_policy; 407 vma_set_policy(tmp, pol); 408 tmp->vm_mm = mm; 409 if (anon_vma_fork(tmp, mpnt)) 410 goto fail_nomem_anon_vma_fork; 411 tmp->vm_flags &= ~VM_LOCKED; 412 tmp->vm_next = tmp->vm_prev = NULL; 413 file = tmp->vm_file; 414 if (file) { 415 struct inode *inode = file->f_path.dentry->d_inode; 416 struct address_space *mapping = file->f_mapping; 417 418 get_file(file); 419 if (tmp->vm_flags & VM_DENYWRITE) 420 atomic_dec(&inode->i_writecount); 421 mutex_lock(&mapping->i_mmap_mutex); 422 if (tmp->vm_flags & VM_SHARED) 423 mapping->i_mmap_writable++; 424 flush_dcache_mmap_lock(mapping); 425 /* insert tmp into the share list, just after mpnt */ 426 vma_prio_tree_add(tmp, mpnt); 427 flush_dcache_mmap_unlock(mapping); 428 mutex_unlock(&mapping->i_mmap_mutex); 429 } 430 431 /* 432 * Clear hugetlb-related page reserves for children. This only 433 * affects MAP_PRIVATE mappings. Faults generated by the child 434 * are not guaranteed to succeed, even if read-only 435 */ 436 if (is_vm_hugetlb_page(tmp)) 437 reset_vma_resv_huge_pages(tmp); 438 439 /* 440 * Link in the new vma and copy the page table entries. 441 */ 442 *pprev = tmp; 443 pprev = &tmp->vm_next; 444 tmp->vm_prev = prev; 445 prev = tmp; 446 447 __vma_link_rb(mm, tmp, rb_link, rb_parent); 448 rb_link = &tmp->vm_rb.rb_right; 449 rb_parent = &tmp->vm_rb; 450 451 mm->map_count++; 452 retval = copy_page_range(mm, oldmm, mpnt); 453 454 if (tmp->vm_ops && tmp->vm_ops->open) 455 tmp->vm_ops->open(tmp); 456 457 if (retval) 458 goto out; 459 } 460 /* a new mm has just been created */ 461 arch_dup_mmap(oldmm, mm); 462 retval = 0; 463 out: 464 up_write(&mm->mmap_sem); 465 flush_tlb_mm(oldmm); 466 up_write(&oldmm->mmap_sem); 467 return retval; 468 fail_nomem_anon_vma_fork: 469 mpol_put(pol); 470 fail_nomem_policy: 471 kmem_cache_free(vm_area_cachep, tmp); 472 fail_nomem: 473 retval = -ENOMEM; 474 vm_unacct_memory(charge); 475 goto out; 476 } 477 478 static inline int mm_alloc_pgd(struct mm_struct *mm) 479 { 480 mm->pgd = pgd_alloc(mm); 481 if (unlikely(!mm->pgd)) 482 return -ENOMEM; 483 return 0; 484 } 485 486 static inline void mm_free_pgd(struct mm_struct *mm) 487 { 488 pgd_free(mm, mm->pgd); 489 } 490 #else 491 #define dup_mmap(mm, oldmm) (0) 492 #define mm_alloc_pgd(mm) (0) 493 #define mm_free_pgd(mm) 494 #endif /* CONFIG_MMU */ 495 496 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 497 498 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 499 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 500 501 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 502 503 static int __init coredump_filter_setup(char *s) 504 { 505 default_dump_filter = 506 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 507 MMF_DUMP_FILTER_MASK; 508 return 1; 509 } 510 511 __setup("coredump_filter=", coredump_filter_setup); 512 513 #include <linux/init_task.h> 514 515 static void mm_init_aio(struct mm_struct *mm) 516 { 517 #ifdef CONFIG_AIO 518 spin_lock_init(&mm->ioctx_lock); 519 INIT_HLIST_HEAD(&mm->ioctx_list); 520 #endif 521 } 522 523 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 524 { 525 atomic_set(&mm->mm_users, 1); 526 atomic_set(&mm->mm_count, 1); 527 init_rwsem(&mm->mmap_sem); 528 INIT_LIST_HEAD(&mm->mmlist); 529 mm->flags = (current->mm) ? 530 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 531 mm->core_state = NULL; 532 mm->nr_ptes = 0; 533 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 534 spin_lock_init(&mm->page_table_lock); 535 mm->free_area_cache = TASK_UNMAPPED_BASE; 536 mm->cached_hole_size = ~0UL; 537 mm_init_aio(mm); 538 mm_init_owner(mm, p); 539 540 if (likely(!mm_alloc_pgd(mm))) { 541 mm->def_flags = 0; 542 mmu_notifier_mm_init(mm); 543 return mm; 544 } 545 546 free_mm(mm); 547 return NULL; 548 } 549 550 static void check_mm(struct mm_struct *mm) 551 { 552 int i; 553 554 for (i = 0; i < NR_MM_COUNTERS; i++) { 555 long x = atomic_long_read(&mm->rss_stat.count[i]); 556 557 if (unlikely(x)) 558 printk(KERN_ALERT "BUG: Bad rss-counter state " 559 "mm:%p idx:%d val:%ld\n", mm, i, x); 560 } 561 562 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 563 VM_BUG_ON(mm->pmd_huge_pte); 564 #endif 565 } 566 567 /* 568 * Allocate and initialize an mm_struct. 569 */ 570 struct mm_struct *mm_alloc(void) 571 { 572 struct mm_struct *mm; 573 574 mm = allocate_mm(); 575 if (!mm) 576 return NULL; 577 578 memset(mm, 0, sizeof(*mm)); 579 mm_init_cpumask(mm); 580 return mm_init(mm, current); 581 } 582 583 /* 584 * Called when the last reference to the mm 585 * is dropped: either by a lazy thread or by 586 * mmput. Free the page directory and the mm. 587 */ 588 void __mmdrop(struct mm_struct *mm) 589 { 590 BUG_ON(mm == &init_mm); 591 mm_free_pgd(mm); 592 destroy_context(mm); 593 mmu_notifier_mm_destroy(mm); 594 check_mm(mm); 595 free_mm(mm); 596 } 597 EXPORT_SYMBOL_GPL(__mmdrop); 598 599 /* 600 * Decrement the use count and release all resources for an mm. 601 */ 602 void mmput(struct mm_struct *mm) 603 { 604 might_sleep(); 605 606 if (atomic_dec_and_test(&mm->mm_users)) { 607 uprobe_clear_state(mm); 608 exit_aio(mm); 609 ksm_exit(mm); 610 khugepaged_exit(mm); /* must run before exit_mmap */ 611 exit_mmap(mm); 612 set_mm_exe_file(mm, NULL); 613 if (!list_empty(&mm->mmlist)) { 614 spin_lock(&mmlist_lock); 615 list_del(&mm->mmlist); 616 spin_unlock(&mmlist_lock); 617 } 618 if (mm->binfmt) 619 module_put(mm->binfmt->module); 620 mmdrop(mm); 621 } 622 } 623 EXPORT_SYMBOL_GPL(mmput); 624 625 /* 626 * We added or removed a vma mapping the executable. The vmas are only mapped 627 * during exec and are not mapped with the mmap system call. 628 * Callers must hold down_write() on the mm's mmap_sem for these 629 */ 630 void added_exe_file_vma(struct mm_struct *mm) 631 { 632 mm->num_exe_file_vmas++; 633 } 634 635 void removed_exe_file_vma(struct mm_struct *mm) 636 { 637 mm->num_exe_file_vmas--; 638 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 639 fput(mm->exe_file); 640 mm->exe_file = NULL; 641 } 642 643 } 644 645 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 646 { 647 if (new_exe_file) 648 get_file(new_exe_file); 649 if (mm->exe_file) 650 fput(mm->exe_file); 651 mm->exe_file = new_exe_file; 652 mm->num_exe_file_vmas = 0; 653 } 654 655 struct file *get_mm_exe_file(struct mm_struct *mm) 656 { 657 struct file *exe_file; 658 659 /* We need mmap_sem to protect against races with removal of 660 * VM_EXECUTABLE vmas */ 661 down_read(&mm->mmap_sem); 662 exe_file = mm->exe_file; 663 if (exe_file) 664 get_file(exe_file); 665 up_read(&mm->mmap_sem); 666 return exe_file; 667 } 668 669 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 670 { 671 /* It's safe to write the exe_file pointer without exe_file_lock because 672 * this is called during fork when the task is not yet in /proc */ 673 newmm->exe_file = get_mm_exe_file(oldmm); 674 } 675 676 /** 677 * get_task_mm - acquire a reference to the task's mm 678 * 679 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 680 * this kernel workthread has transiently adopted a user mm with use_mm, 681 * to do its AIO) is not set and if so returns a reference to it, after 682 * bumping up the use count. User must release the mm via mmput() 683 * after use. Typically used by /proc and ptrace. 684 */ 685 struct mm_struct *get_task_mm(struct task_struct *task) 686 { 687 struct mm_struct *mm; 688 689 task_lock(task); 690 mm = task->mm; 691 if (mm) { 692 if (task->flags & PF_KTHREAD) 693 mm = NULL; 694 else 695 atomic_inc(&mm->mm_users); 696 } 697 task_unlock(task); 698 return mm; 699 } 700 EXPORT_SYMBOL_GPL(get_task_mm); 701 702 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 703 { 704 struct mm_struct *mm; 705 int err; 706 707 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 708 if (err) 709 return ERR_PTR(err); 710 711 mm = get_task_mm(task); 712 if (mm && mm != current->mm && 713 !ptrace_may_access(task, mode)) { 714 mmput(mm); 715 mm = ERR_PTR(-EACCES); 716 } 717 mutex_unlock(&task->signal->cred_guard_mutex); 718 719 return mm; 720 } 721 722 static void complete_vfork_done(struct task_struct *tsk) 723 { 724 struct completion *vfork; 725 726 task_lock(tsk); 727 vfork = tsk->vfork_done; 728 if (likely(vfork)) { 729 tsk->vfork_done = NULL; 730 complete(vfork); 731 } 732 task_unlock(tsk); 733 } 734 735 static int wait_for_vfork_done(struct task_struct *child, 736 struct completion *vfork) 737 { 738 int killed; 739 740 freezer_do_not_count(); 741 killed = wait_for_completion_killable(vfork); 742 freezer_count(); 743 744 if (killed) { 745 task_lock(child); 746 child->vfork_done = NULL; 747 task_unlock(child); 748 } 749 750 put_task_struct(child); 751 return killed; 752 } 753 754 /* Please note the differences between mmput and mm_release. 755 * mmput is called whenever we stop holding onto a mm_struct, 756 * error success whatever. 757 * 758 * mm_release is called after a mm_struct has been removed 759 * from the current process. 760 * 761 * This difference is important for error handling, when we 762 * only half set up a mm_struct for a new process and need to restore 763 * the old one. Because we mmput the new mm_struct before 764 * restoring the old one. . . 765 * Eric Biederman 10 January 1998 766 */ 767 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 768 { 769 /* Get rid of any futexes when releasing the mm */ 770 #ifdef CONFIG_FUTEX 771 if (unlikely(tsk->robust_list)) { 772 exit_robust_list(tsk); 773 tsk->robust_list = NULL; 774 } 775 #ifdef CONFIG_COMPAT 776 if (unlikely(tsk->compat_robust_list)) { 777 compat_exit_robust_list(tsk); 778 tsk->compat_robust_list = NULL; 779 } 780 #endif 781 if (unlikely(!list_empty(&tsk->pi_state_list))) 782 exit_pi_state_list(tsk); 783 #endif 784 785 uprobe_free_utask(tsk); 786 787 /* Get rid of any cached register state */ 788 deactivate_mm(tsk, mm); 789 790 /* 791 * If we're exiting normally, clear a user-space tid field if 792 * requested. We leave this alone when dying by signal, to leave 793 * the value intact in a core dump, and to save the unnecessary 794 * trouble, say, a killed vfork parent shouldn't touch this mm. 795 * Userland only wants this done for a sys_exit. 796 */ 797 if (tsk->clear_child_tid) { 798 if (!(tsk->flags & PF_SIGNALED) && 799 atomic_read(&mm->mm_users) > 1) { 800 /* 801 * We don't check the error code - if userspace has 802 * not set up a proper pointer then tough luck. 803 */ 804 put_user(0, tsk->clear_child_tid); 805 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 806 1, NULL, NULL, 0); 807 } 808 tsk->clear_child_tid = NULL; 809 } 810 811 /* 812 * All done, finally we can wake up parent and return this mm to him. 813 * Also kthread_stop() uses this completion for synchronization. 814 */ 815 if (tsk->vfork_done) 816 complete_vfork_done(tsk); 817 } 818 819 /* 820 * Allocate a new mm structure and copy contents from the 821 * mm structure of the passed in task structure. 822 */ 823 struct mm_struct *dup_mm(struct task_struct *tsk) 824 { 825 struct mm_struct *mm, *oldmm = current->mm; 826 int err; 827 828 if (!oldmm) 829 return NULL; 830 831 mm = allocate_mm(); 832 if (!mm) 833 goto fail_nomem; 834 835 memcpy(mm, oldmm, sizeof(*mm)); 836 mm_init_cpumask(mm); 837 838 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 839 mm->pmd_huge_pte = NULL; 840 #endif 841 if (!mm_init(mm, tsk)) 842 goto fail_nomem; 843 844 if (init_new_context(tsk, mm)) 845 goto fail_nocontext; 846 847 dup_mm_exe_file(oldmm, mm); 848 849 err = dup_mmap(mm, oldmm); 850 if (err) 851 goto free_pt; 852 853 mm->hiwater_rss = get_mm_rss(mm); 854 mm->hiwater_vm = mm->total_vm; 855 856 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 857 goto free_pt; 858 859 return mm; 860 861 free_pt: 862 /* don't put binfmt in mmput, we haven't got module yet */ 863 mm->binfmt = NULL; 864 mmput(mm); 865 866 fail_nomem: 867 return NULL; 868 869 fail_nocontext: 870 /* 871 * If init_new_context() failed, we cannot use mmput() to free the mm 872 * because it calls destroy_context() 873 */ 874 mm_free_pgd(mm); 875 free_mm(mm); 876 return NULL; 877 } 878 879 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 880 { 881 struct mm_struct *mm, *oldmm; 882 int retval; 883 884 tsk->min_flt = tsk->maj_flt = 0; 885 tsk->nvcsw = tsk->nivcsw = 0; 886 #ifdef CONFIG_DETECT_HUNG_TASK 887 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 888 #endif 889 890 tsk->mm = NULL; 891 tsk->active_mm = NULL; 892 893 /* 894 * Are we cloning a kernel thread? 895 * 896 * We need to steal a active VM for that.. 897 */ 898 oldmm = current->mm; 899 if (!oldmm) 900 return 0; 901 902 if (clone_flags & CLONE_VM) { 903 atomic_inc(&oldmm->mm_users); 904 mm = oldmm; 905 goto good_mm; 906 } 907 908 retval = -ENOMEM; 909 mm = dup_mm(tsk); 910 if (!mm) 911 goto fail_nomem; 912 913 good_mm: 914 tsk->mm = mm; 915 tsk->active_mm = mm; 916 return 0; 917 918 fail_nomem: 919 return retval; 920 } 921 922 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 923 { 924 struct fs_struct *fs = current->fs; 925 if (clone_flags & CLONE_FS) { 926 /* tsk->fs is already what we want */ 927 spin_lock(&fs->lock); 928 if (fs->in_exec) { 929 spin_unlock(&fs->lock); 930 return -EAGAIN; 931 } 932 fs->users++; 933 spin_unlock(&fs->lock); 934 return 0; 935 } 936 tsk->fs = copy_fs_struct(fs); 937 if (!tsk->fs) 938 return -ENOMEM; 939 return 0; 940 } 941 942 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 943 { 944 struct files_struct *oldf, *newf; 945 int error = 0; 946 947 /* 948 * A background process may not have any files ... 949 */ 950 oldf = current->files; 951 if (!oldf) 952 goto out; 953 954 if (clone_flags & CLONE_FILES) { 955 atomic_inc(&oldf->count); 956 goto out; 957 } 958 959 newf = dup_fd(oldf, &error); 960 if (!newf) 961 goto out; 962 963 tsk->files = newf; 964 error = 0; 965 out: 966 return error; 967 } 968 969 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 970 { 971 #ifdef CONFIG_BLOCK 972 struct io_context *ioc = current->io_context; 973 struct io_context *new_ioc; 974 975 if (!ioc) 976 return 0; 977 /* 978 * Share io context with parent, if CLONE_IO is set 979 */ 980 if (clone_flags & CLONE_IO) { 981 ioc_task_link(ioc); 982 tsk->io_context = ioc; 983 } else if (ioprio_valid(ioc->ioprio)) { 984 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 985 if (unlikely(!new_ioc)) 986 return -ENOMEM; 987 988 new_ioc->ioprio = ioc->ioprio; 989 put_io_context(new_ioc); 990 } 991 #endif 992 return 0; 993 } 994 995 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 996 { 997 struct sighand_struct *sig; 998 999 if (clone_flags & CLONE_SIGHAND) { 1000 atomic_inc(¤t->sighand->count); 1001 return 0; 1002 } 1003 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1004 rcu_assign_pointer(tsk->sighand, sig); 1005 if (!sig) 1006 return -ENOMEM; 1007 atomic_set(&sig->count, 1); 1008 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1009 return 0; 1010 } 1011 1012 void __cleanup_sighand(struct sighand_struct *sighand) 1013 { 1014 if (atomic_dec_and_test(&sighand->count)) { 1015 signalfd_cleanup(sighand); 1016 kmem_cache_free(sighand_cachep, sighand); 1017 } 1018 } 1019 1020 1021 /* 1022 * Initialize POSIX timer handling for a thread group. 1023 */ 1024 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1025 { 1026 unsigned long cpu_limit; 1027 1028 /* Thread group counters. */ 1029 thread_group_cputime_init(sig); 1030 1031 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1032 if (cpu_limit != RLIM_INFINITY) { 1033 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1034 sig->cputimer.running = 1; 1035 } 1036 1037 /* The timer lists. */ 1038 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1039 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1040 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1041 } 1042 1043 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1044 { 1045 struct signal_struct *sig; 1046 1047 if (clone_flags & CLONE_THREAD) 1048 return 0; 1049 1050 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1051 tsk->signal = sig; 1052 if (!sig) 1053 return -ENOMEM; 1054 1055 sig->nr_threads = 1; 1056 atomic_set(&sig->live, 1); 1057 atomic_set(&sig->sigcnt, 1); 1058 init_waitqueue_head(&sig->wait_chldexit); 1059 if (clone_flags & CLONE_NEWPID) 1060 sig->flags |= SIGNAL_UNKILLABLE; 1061 sig->curr_target = tsk; 1062 init_sigpending(&sig->shared_pending); 1063 INIT_LIST_HEAD(&sig->posix_timers); 1064 1065 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1066 sig->real_timer.function = it_real_fn; 1067 1068 task_lock(current->group_leader); 1069 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1070 task_unlock(current->group_leader); 1071 1072 posix_cpu_timers_init_group(sig); 1073 1074 tty_audit_fork(sig); 1075 sched_autogroup_fork(sig); 1076 1077 #ifdef CONFIG_CGROUPS 1078 init_rwsem(&sig->group_rwsem); 1079 #endif 1080 1081 sig->oom_adj = current->signal->oom_adj; 1082 sig->oom_score_adj = current->signal->oom_score_adj; 1083 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1084 1085 sig->has_child_subreaper = current->signal->has_child_subreaper || 1086 current->signal->is_child_subreaper; 1087 1088 mutex_init(&sig->cred_guard_mutex); 1089 1090 return 0; 1091 } 1092 1093 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1094 { 1095 unsigned long new_flags = p->flags; 1096 1097 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1098 new_flags |= PF_FORKNOEXEC; 1099 p->flags = new_flags; 1100 } 1101 1102 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1103 { 1104 current->clear_child_tid = tidptr; 1105 1106 return task_pid_vnr(current); 1107 } 1108 1109 static void rt_mutex_init_task(struct task_struct *p) 1110 { 1111 raw_spin_lock_init(&p->pi_lock); 1112 #ifdef CONFIG_RT_MUTEXES 1113 plist_head_init(&p->pi_waiters); 1114 p->pi_blocked_on = NULL; 1115 #endif 1116 } 1117 1118 #ifdef CONFIG_MM_OWNER 1119 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1120 { 1121 mm->owner = p; 1122 } 1123 #endif /* CONFIG_MM_OWNER */ 1124 1125 /* 1126 * Initialize POSIX timer handling for a single task. 1127 */ 1128 static void posix_cpu_timers_init(struct task_struct *tsk) 1129 { 1130 tsk->cputime_expires.prof_exp = 0; 1131 tsk->cputime_expires.virt_exp = 0; 1132 tsk->cputime_expires.sched_exp = 0; 1133 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1134 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1135 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1136 } 1137 1138 /* 1139 * This creates a new process as a copy of the old one, 1140 * but does not actually start it yet. 1141 * 1142 * It copies the registers, and all the appropriate 1143 * parts of the process environment (as per the clone 1144 * flags). The actual kick-off is left to the caller. 1145 */ 1146 static struct task_struct *copy_process(unsigned long clone_flags, 1147 unsigned long stack_start, 1148 struct pt_regs *regs, 1149 unsigned long stack_size, 1150 int __user *child_tidptr, 1151 struct pid *pid, 1152 int trace) 1153 { 1154 int retval; 1155 struct task_struct *p; 1156 int cgroup_callbacks_done = 0; 1157 1158 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1159 return ERR_PTR(-EINVAL); 1160 1161 /* 1162 * Thread groups must share signals as well, and detached threads 1163 * can only be started up within the thread group. 1164 */ 1165 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1166 return ERR_PTR(-EINVAL); 1167 1168 /* 1169 * Shared signal handlers imply shared VM. By way of the above, 1170 * thread groups also imply shared VM. Blocking this case allows 1171 * for various simplifications in other code. 1172 */ 1173 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1174 return ERR_PTR(-EINVAL); 1175 1176 /* 1177 * Siblings of global init remain as zombies on exit since they are 1178 * not reaped by their parent (swapper). To solve this and to avoid 1179 * multi-rooted process trees, prevent global and container-inits 1180 * from creating siblings. 1181 */ 1182 if ((clone_flags & CLONE_PARENT) && 1183 current->signal->flags & SIGNAL_UNKILLABLE) 1184 return ERR_PTR(-EINVAL); 1185 1186 retval = security_task_create(clone_flags); 1187 if (retval) 1188 goto fork_out; 1189 1190 retval = -ENOMEM; 1191 p = dup_task_struct(current); 1192 if (!p) 1193 goto fork_out; 1194 1195 ftrace_graph_init_task(p); 1196 get_seccomp_filter(p); 1197 1198 rt_mutex_init_task(p); 1199 1200 #ifdef CONFIG_PROVE_LOCKING 1201 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1202 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1203 #endif 1204 retval = -EAGAIN; 1205 if (atomic_read(&p->real_cred->user->processes) >= 1206 task_rlimit(p, RLIMIT_NPROC)) { 1207 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1208 p->real_cred->user != INIT_USER) 1209 goto bad_fork_free; 1210 } 1211 current->flags &= ~PF_NPROC_EXCEEDED; 1212 1213 retval = copy_creds(p, clone_flags); 1214 if (retval < 0) 1215 goto bad_fork_free; 1216 1217 /* 1218 * If multiple threads are within copy_process(), then this check 1219 * triggers too late. This doesn't hurt, the check is only there 1220 * to stop root fork bombs. 1221 */ 1222 retval = -EAGAIN; 1223 if (nr_threads >= max_threads) 1224 goto bad_fork_cleanup_count; 1225 1226 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1227 goto bad_fork_cleanup_count; 1228 1229 p->did_exec = 0; 1230 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1231 copy_flags(clone_flags, p); 1232 INIT_LIST_HEAD(&p->children); 1233 INIT_LIST_HEAD(&p->sibling); 1234 rcu_copy_process(p); 1235 p->vfork_done = NULL; 1236 spin_lock_init(&p->alloc_lock); 1237 1238 init_sigpending(&p->pending); 1239 1240 p->utime = p->stime = p->gtime = 0; 1241 p->utimescaled = p->stimescaled = 0; 1242 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1243 p->prev_utime = p->prev_stime = 0; 1244 #endif 1245 #if defined(SPLIT_RSS_COUNTING) 1246 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1247 #endif 1248 1249 p->default_timer_slack_ns = current->timer_slack_ns; 1250 1251 task_io_accounting_init(&p->ioac); 1252 acct_clear_integrals(p); 1253 1254 posix_cpu_timers_init(p); 1255 1256 do_posix_clock_monotonic_gettime(&p->start_time); 1257 p->real_start_time = p->start_time; 1258 monotonic_to_bootbased(&p->real_start_time); 1259 p->io_context = NULL; 1260 p->audit_context = NULL; 1261 if (clone_flags & CLONE_THREAD) 1262 threadgroup_change_begin(current); 1263 cgroup_fork(p); 1264 #ifdef CONFIG_NUMA 1265 p->mempolicy = mpol_dup(p->mempolicy); 1266 if (IS_ERR(p->mempolicy)) { 1267 retval = PTR_ERR(p->mempolicy); 1268 p->mempolicy = NULL; 1269 goto bad_fork_cleanup_cgroup; 1270 } 1271 mpol_fix_fork_child_flag(p); 1272 #endif 1273 #ifdef CONFIG_CPUSETS 1274 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1275 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1276 seqcount_init(&p->mems_allowed_seq); 1277 #endif 1278 #ifdef CONFIG_TRACE_IRQFLAGS 1279 p->irq_events = 0; 1280 p->hardirqs_enabled = 0; 1281 p->hardirq_enable_ip = 0; 1282 p->hardirq_enable_event = 0; 1283 p->hardirq_disable_ip = _THIS_IP_; 1284 p->hardirq_disable_event = 0; 1285 p->softirqs_enabled = 1; 1286 p->softirq_enable_ip = _THIS_IP_; 1287 p->softirq_enable_event = 0; 1288 p->softirq_disable_ip = 0; 1289 p->softirq_disable_event = 0; 1290 p->hardirq_context = 0; 1291 p->softirq_context = 0; 1292 #endif 1293 #ifdef CONFIG_LOCKDEP 1294 p->lockdep_depth = 0; /* no locks held yet */ 1295 p->curr_chain_key = 0; 1296 p->lockdep_recursion = 0; 1297 #endif 1298 1299 #ifdef CONFIG_DEBUG_MUTEXES 1300 p->blocked_on = NULL; /* not blocked yet */ 1301 #endif 1302 #ifdef CONFIG_MEMCG 1303 p->memcg_batch.do_batch = 0; 1304 p->memcg_batch.memcg = NULL; 1305 #endif 1306 1307 /* Perform scheduler related setup. Assign this task to a CPU. */ 1308 sched_fork(p); 1309 1310 retval = perf_event_init_task(p); 1311 if (retval) 1312 goto bad_fork_cleanup_policy; 1313 retval = audit_alloc(p); 1314 if (retval) 1315 goto bad_fork_cleanup_policy; 1316 /* copy all the process information */ 1317 retval = copy_semundo(clone_flags, p); 1318 if (retval) 1319 goto bad_fork_cleanup_audit; 1320 retval = copy_files(clone_flags, p); 1321 if (retval) 1322 goto bad_fork_cleanup_semundo; 1323 retval = copy_fs(clone_flags, p); 1324 if (retval) 1325 goto bad_fork_cleanup_files; 1326 retval = copy_sighand(clone_flags, p); 1327 if (retval) 1328 goto bad_fork_cleanup_fs; 1329 retval = copy_signal(clone_flags, p); 1330 if (retval) 1331 goto bad_fork_cleanup_sighand; 1332 retval = copy_mm(clone_flags, p); 1333 if (retval) 1334 goto bad_fork_cleanup_signal; 1335 retval = copy_namespaces(clone_flags, p); 1336 if (retval) 1337 goto bad_fork_cleanup_mm; 1338 retval = copy_io(clone_flags, p); 1339 if (retval) 1340 goto bad_fork_cleanup_namespaces; 1341 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1342 if (retval) 1343 goto bad_fork_cleanup_io; 1344 1345 if (pid != &init_struct_pid) { 1346 retval = -ENOMEM; 1347 pid = alloc_pid(p->nsproxy->pid_ns); 1348 if (!pid) 1349 goto bad_fork_cleanup_io; 1350 } 1351 1352 p->pid = pid_nr(pid); 1353 p->tgid = p->pid; 1354 if (clone_flags & CLONE_THREAD) 1355 p->tgid = current->tgid; 1356 1357 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1358 /* 1359 * Clear TID on mm_release()? 1360 */ 1361 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1362 #ifdef CONFIG_BLOCK 1363 p->plug = NULL; 1364 #endif 1365 #ifdef CONFIG_FUTEX 1366 p->robust_list = NULL; 1367 #ifdef CONFIG_COMPAT 1368 p->compat_robust_list = NULL; 1369 #endif 1370 INIT_LIST_HEAD(&p->pi_state_list); 1371 p->pi_state_cache = NULL; 1372 #endif 1373 uprobe_copy_process(p); 1374 /* 1375 * sigaltstack should be cleared when sharing the same VM 1376 */ 1377 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1378 p->sas_ss_sp = p->sas_ss_size = 0; 1379 1380 /* 1381 * Syscall tracing and stepping should be turned off in the 1382 * child regardless of CLONE_PTRACE. 1383 */ 1384 user_disable_single_step(p); 1385 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1386 #ifdef TIF_SYSCALL_EMU 1387 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1388 #endif 1389 clear_all_latency_tracing(p); 1390 1391 /* ok, now we should be set up.. */ 1392 if (clone_flags & CLONE_THREAD) 1393 p->exit_signal = -1; 1394 else if (clone_flags & CLONE_PARENT) 1395 p->exit_signal = current->group_leader->exit_signal; 1396 else 1397 p->exit_signal = (clone_flags & CSIGNAL); 1398 1399 p->pdeath_signal = 0; 1400 p->exit_state = 0; 1401 1402 p->nr_dirtied = 0; 1403 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1404 p->dirty_paused_when = 0; 1405 1406 /* 1407 * Ok, make it visible to the rest of the system. 1408 * We dont wake it up yet. 1409 */ 1410 p->group_leader = p; 1411 INIT_LIST_HEAD(&p->thread_group); 1412 p->task_works = NULL; 1413 1414 /* Now that the task is set up, run cgroup callbacks if 1415 * necessary. We need to run them before the task is visible 1416 * on the tasklist. */ 1417 cgroup_fork_callbacks(p); 1418 cgroup_callbacks_done = 1; 1419 1420 /* Need tasklist lock for parent etc handling! */ 1421 write_lock_irq(&tasklist_lock); 1422 1423 /* CLONE_PARENT re-uses the old parent */ 1424 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1425 p->real_parent = current->real_parent; 1426 p->parent_exec_id = current->parent_exec_id; 1427 } else { 1428 p->real_parent = current; 1429 p->parent_exec_id = current->self_exec_id; 1430 } 1431 1432 spin_lock(¤t->sighand->siglock); 1433 1434 /* 1435 * Process group and session signals need to be delivered to just the 1436 * parent before the fork or both the parent and the child after the 1437 * fork. Restart if a signal comes in before we add the new process to 1438 * it's process group. 1439 * A fatal signal pending means that current will exit, so the new 1440 * thread can't slip out of an OOM kill (or normal SIGKILL). 1441 */ 1442 recalc_sigpending(); 1443 if (signal_pending(current)) { 1444 spin_unlock(¤t->sighand->siglock); 1445 write_unlock_irq(&tasklist_lock); 1446 retval = -ERESTARTNOINTR; 1447 goto bad_fork_free_pid; 1448 } 1449 1450 if (clone_flags & CLONE_THREAD) { 1451 current->signal->nr_threads++; 1452 atomic_inc(¤t->signal->live); 1453 atomic_inc(¤t->signal->sigcnt); 1454 p->group_leader = current->group_leader; 1455 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1456 } 1457 1458 if (likely(p->pid)) { 1459 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1460 1461 if (thread_group_leader(p)) { 1462 if (is_child_reaper(pid)) 1463 p->nsproxy->pid_ns->child_reaper = p; 1464 1465 p->signal->leader_pid = pid; 1466 p->signal->tty = tty_kref_get(current->signal->tty); 1467 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1468 attach_pid(p, PIDTYPE_SID, task_session(current)); 1469 list_add_tail(&p->sibling, &p->real_parent->children); 1470 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1471 __this_cpu_inc(process_counts); 1472 } 1473 attach_pid(p, PIDTYPE_PID, pid); 1474 nr_threads++; 1475 } 1476 1477 total_forks++; 1478 spin_unlock(¤t->sighand->siglock); 1479 write_unlock_irq(&tasklist_lock); 1480 proc_fork_connector(p); 1481 cgroup_post_fork(p); 1482 if (clone_flags & CLONE_THREAD) 1483 threadgroup_change_end(current); 1484 perf_event_fork(p); 1485 1486 trace_task_newtask(p, clone_flags); 1487 1488 return p; 1489 1490 bad_fork_free_pid: 1491 if (pid != &init_struct_pid) 1492 free_pid(pid); 1493 bad_fork_cleanup_io: 1494 if (p->io_context) 1495 exit_io_context(p); 1496 bad_fork_cleanup_namespaces: 1497 if (unlikely(clone_flags & CLONE_NEWPID)) 1498 pid_ns_release_proc(p->nsproxy->pid_ns); 1499 exit_task_namespaces(p); 1500 bad_fork_cleanup_mm: 1501 if (p->mm) 1502 mmput(p->mm); 1503 bad_fork_cleanup_signal: 1504 if (!(clone_flags & CLONE_THREAD)) 1505 free_signal_struct(p->signal); 1506 bad_fork_cleanup_sighand: 1507 __cleanup_sighand(p->sighand); 1508 bad_fork_cleanup_fs: 1509 exit_fs(p); /* blocking */ 1510 bad_fork_cleanup_files: 1511 exit_files(p); /* blocking */ 1512 bad_fork_cleanup_semundo: 1513 exit_sem(p); 1514 bad_fork_cleanup_audit: 1515 audit_free(p); 1516 bad_fork_cleanup_policy: 1517 perf_event_free_task(p); 1518 #ifdef CONFIG_NUMA 1519 mpol_put(p->mempolicy); 1520 bad_fork_cleanup_cgroup: 1521 #endif 1522 if (clone_flags & CLONE_THREAD) 1523 threadgroup_change_end(current); 1524 cgroup_exit(p, cgroup_callbacks_done); 1525 delayacct_tsk_free(p); 1526 module_put(task_thread_info(p)->exec_domain->module); 1527 bad_fork_cleanup_count: 1528 atomic_dec(&p->cred->user->processes); 1529 exit_creds(p); 1530 bad_fork_free: 1531 free_task(p); 1532 fork_out: 1533 return ERR_PTR(retval); 1534 } 1535 1536 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1537 { 1538 memset(regs, 0, sizeof(struct pt_regs)); 1539 return regs; 1540 } 1541 1542 static inline void init_idle_pids(struct pid_link *links) 1543 { 1544 enum pid_type type; 1545 1546 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1547 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1548 links[type].pid = &init_struct_pid; 1549 } 1550 } 1551 1552 struct task_struct * __cpuinit fork_idle(int cpu) 1553 { 1554 struct task_struct *task; 1555 struct pt_regs regs; 1556 1557 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1558 &init_struct_pid, 0); 1559 if (!IS_ERR(task)) { 1560 init_idle_pids(task->pids); 1561 init_idle(task, cpu); 1562 } 1563 1564 return task; 1565 } 1566 1567 /* 1568 * Ok, this is the main fork-routine. 1569 * 1570 * It copies the process, and if successful kick-starts 1571 * it and waits for it to finish using the VM if required. 1572 */ 1573 long do_fork(unsigned long clone_flags, 1574 unsigned long stack_start, 1575 struct pt_regs *regs, 1576 unsigned long stack_size, 1577 int __user *parent_tidptr, 1578 int __user *child_tidptr) 1579 { 1580 struct task_struct *p; 1581 int trace = 0; 1582 long nr; 1583 1584 /* 1585 * Do some preliminary argument and permissions checking before we 1586 * actually start allocating stuff 1587 */ 1588 if (clone_flags & CLONE_NEWUSER) { 1589 if (clone_flags & CLONE_THREAD) 1590 return -EINVAL; 1591 /* hopefully this check will go away when userns support is 1592 * complete 1593 */ 1594 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1595 !capable(CAP_SETGID)) 1596 return -EPERM; 1597 } 1598 1599 /* 1600 * Determine whether and which event to report to ptracer. When 1601 * called from kernel_thread or CLONE_UNTRACED is explicitly 1602 * requested, no event is reported; otherwise, report if the event 1603 * for the type of forking is enabled. 1604 */ 1605 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1606 if (clone_flags & CLONE_VFORK) 1607 trace = PTRACE_EVENT_VFORK; 1608 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1609 trace = PTRACE_EVENT_CLONE; 1610 else 1611 trace = PTRACE_EVENT_FORK; 1612 1613 if (likely(!ptrace_event_enabled(current, trace))) 1614 trace = 0; 1615 } 1616 1617 p = copy_process(clone_flags, stack_start, regs, stack_size, 1618 child_tidptr, NULL, trace); 1619 /* 1620 * Do this prior waking up the new thread - the thread pointer 1621 * might get invalid after that point, if the thread exits quickly. 1622 */ 1623 if (!IS_ERR(p)) { 1624 struct completion vfork; 1625 1626 trace_sched_process_fork(current, p); 1627 1628 nr = task_pid_vnr(p); 1629 1630 if (clone_flags & CLONE_PARENT_SETTID) 1631 put_user(nr, parent_tidptr); 1632 1633 if (clone_flags & CLONE_VFORK) { 1634 p->vfork_done = &vfork; 1635 init_completion(&vfork); 1636 get_task_struct(p); 1637 } 1638 1639 wake_up_new_task(p); 1640 1641 /* forking complete and child started to run, tell ptracer */ 1642 if (unlikely(trace)) 1643 ptrace_event(trace, nr); 1644 1645 if (clone_flags & CLONE_VFORK) { 1646 if (!wait_for_vfork_done(p, &vfork)) 1647 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1648 } 1649 } else { 1650 nr = PTR_ERR(p); 1651 } 1652 return nr; 1653 } 1654 1655 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1656 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1657 #endif 1658 1659 static void sighand_ctor(void *data) 1660 { 1661 struct sighand_struct *sighand = data; 1662 1663 spin_lock_init(&sighand->siglock); 1664 init_waitqueue_head(&sighand->signalfd_wqh); 1665 } 1666 1667 void __init proc_caches_init(void) 1668 { 1669 sighand_cachep = kmem_cache_create("sighand_cache", 1670 sizeof(struct sighand_struct), 0, 1671 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1672 SLAB_NOTRACK, sighand_ctor); 1673 signal_cachep = kmem_cache_create("signal_cache", 1674 sizeof(struct signal_struct), 0, 1675 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1676 files_cachep = kmem_cache_create("files_cache", 1677 sizeof(struct files_struct), 0, 1678 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1679 fs_cachep = kmem_cache_create("fs_cache", 1680 sizeof(struct fs_struct), 0, 1681 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1682 /* 1683 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1684 * whole struct cpumask for the OFFSTACK case. We could change 1685 * this to *only* allocate as much of it as required by the 1686 * maximum number of CPU's we can ever have. The cpumask_allocation 1687 * is at the end of the structure, exactly for that reason. 1688 */ 1689 mm_cachep = kmem_cache_create("mm_struct", 1690 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1691 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1692 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1693 mmap_init(); 1694 nsproxy_cache_init(); 1695 } 1696 1697 /* 1698 * Check constraints on flags passed to the unshare system call. 1699 */ 1700 static int check_unshare_flags(unsigned long unshare_flags) 1701 { 1702 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1703 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1704 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1705 return -EINVAL; 1706 /* 1707 * Not implemented, but pretend it works if there is nothing to 1708 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1709 * needs to unshare vm. 1710 */ 1711 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1712 /* FIXME: get_task_mm() increments ->mm_users */ 1713 if (atomic_read(¤t->mm->mm_users) > 1) 1714 return -EINVAL; 1715 } 1716 1717 return 0; 1718 } 1719 1720 /* 1721 * Unshare the filesystem structure if it is being shared 1722 */ 1723 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1724 { 1725 struct fs_struct *fs = current->fs; 1726 1727 if (!(unshare_flags & CLONE_FS) || !fs) 1728 return 0; 1729 1730 /* don't need lock here; in the worst case we'll do useless copy */ 1731 if (fs->users == 1) 1732 return 0; 1733 1734 *new_fsp = copy_fs_struct(fs); 1735 if (!*new_fsp) 1736 return -ENOMEM; 1737 1738 return 0; 1739 } 1740 1741 /* 1742 * Unshare file descriptor table if it is being shared 1743 */ 1744 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1745 { 1746 struct files_struct *fd = current->files; 1747 int error = 0; 1748 1749 if ((unshare_flags & CLONE_FILES) && 1750 (fd && atomic_read(&fd->count) > 1)) { 1751 *new_fdp = dup_fd(fd, &error); 1752 if (!*new_fdp) 1753 return error; 1754 } 1755 1756 return 0; 1757 } 1758 1759 /* 1760 * unshare allows a process to 'unshare' part of the process 1761 * context which was originally shared using clone. copy_* 1762 * functions used by do_fork() cannot be used here directly 1763 * because they modify an inactive task_struct that is being 1764 * constructed. Here we are modifying the current, active, 1765 * task_struct. 1766 */ 1767 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1768 { 1769 struct fs_struct *fs, *new_fs = NULL; 1770 struct files_struct *fd, *new_fd = NULL; 1771 struct nsproxy *new_nsproxy = NULL; 1772 int do_sysvsem = 0; 1773 int err; 1774 1775 err = check_unshare_flags(unshare_flags); 1776 if (err) 1777 goto bad_unshare_out; 1778 1779 /* 1780 * If unsharing namespace, must also unshare filesystem information. 1781 */ 1782 if (unshare_flags & CLONE_NEWNS) 1783 unshare_flags |= CLONE_FS; 1784 /* 1785 * CLONE_NEWIPC must also detach from the undolist: after switching 1786 * to a new ipc namespace, the semaphore arrays from the old 1787 * namespace are unreachable. 1788 */ 1789 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1790 do_sysvsem = 1; 1791 err = unshare_fs(unshare_flags, &new_fs); 1792 if (err) 1793 goto bad_unshare_out; 1794 err = unshare_fd(unshare_flags, &new_fd); 1795 if (err) 1796 goto bad_unshare_cleanup_fs; 1797 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1798 if (err) 1799 goto bad_unshare_cleanup_fd; 1800 1801 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1802 if (do_sysvsem) { 1803 /* 1804 * CLONE_SYSVSEM is equivalent to sys_exit(). 1805 */ 1806 exit_sem(current); 1807 } 1808 1809 if (new_nsproxy) { 1810 switch_task_namespaces(current, new_nsproxy); 1811 new_nsproxy = NULL; 1812 } 1813 1814 task_lock(current); 1815 1816 if (new_fs) { 1817 fs = current->fs; 1818 spin_lock(&fs->lock); 1819 current->fs = new_fs; 1820 if (--fs->users) 1821 new_fs = NULL; 1822 else 1823 new_fs = fs; 1824 spin_unlock(&fs->lock); 1825 } 1826 1827 if (new_fd) { 1828 fd = current->files; 1829 current->files = new_fd; 1830 new_fd = fd; 1831 } 1832 1833 task_unlock(current); 1834 } 1835 1836 if (new_nsproxy) 1837 put_nsproxy(new_nsproxy); 1838 1839 bad_unshare_cleanup_fd: 1840 if (new_fd) 1841 put_files_struct(new_fd); 1842 1843 bad_unshare_cleanup_fs: 1844 if (new_fs) 1845 free_fs_struct(new_fs); 1846 1847 bad_unshare_out: 1848 return err; 1849 } 1850 1851 /* 1852 * Helper to unshare the files of the current task. 1853 * We don't want to expose copy_files internals to 1854 * the exec layer of the kernel. 1855 */ 1856 1857 int unshare_files(struct files_struct **displaced) 1858 { 1859 struct task_struct *task = current; 1860 struct files_struct *copy = NULL; 1861 int error; 1862 1863 error = unshare_fd(CLONE_FILES, ©); 1864 if (error || !copy) { 1865 *displaced = NULL; 1866 return error; 1867 } 1868 *displaced = task->files; 1869 task_lock(task); 1870 task->files = copy; 1871 task_unlock(task); 1872 return 0; 1873 } 1874